ABSTRACT
The immunotoxic effect of repeated sublethal doses of trichlorfon was studiedby using 512 male Lewis mice. They were divided into 4 control groups [n =32] received distilled water and 4 test groups [n = 96] received trichlorfon[an organophosphorous insecticide] in daily oral doses for 15, 30, 45 and 60days, respectively. Each test group was divided into 3 equal subgroupsaccording to trichlorfon dose [30, 60 and 90 mg/kg body weight, respectively]. The degree of immunotoxicity was studied by determining serum immunoglobulinsconcentrations, the percentage of lymphocyte blastogenesis, phagocyticpercentage and index. The phagocytic percentage showed a significantreduction with low dose for 45 and 60 days and for all durations with mediumand high doses. Phagocytic index reduction following the low dose for 30, 45and 60 days was significant and for all durations with medium and high doses